High vacuum valves



Nov. 1, 1966 J. T. MARK HIGH VACUUM VALVES Original Filed Sept. 22, 1959 2 Sheets-Sheet 1 INVENTOR.

JOHN T. MARK BY wmDmmwma m3 omoDamm LO mumnom E mm 3 mEDwwwma J. T. MARK HIGH VACUUM VALVES Nov. 1, 1966 Original Filed Sept. 22, 1959 2 Sheets-Sheet 2 Fig. 4

I'NVENTOR.

JOHN T. MARK United States Patent Office 3,282,276 Patented Nov. 1, 1966 3,282,276 HIGH VACUUM VALVES John T. Mark, Lancaster, Pa, assignor, by mesne assignments, to the United States of America as represented by the United States Atomic Energy Commission Continuation of application Ser. No. 841,643, Sept. 22,

1959. This application May 5, 1965, Ser. No. 453,531 1 Claim. (Cl. 137-1) This application is a continuation of my co-pending application Serial No. 841,643, filed September 22, 1959, for High Vacuum Valves, now abandoned.

The present invention relates to valves, and particularly to valves adapted selectively to effect closure of and communication with a region having a reduced gas pressure. This invention was made in the course of, or under a contract with, the United States Atomic Energy Commission.

In certain applications it is desirable to have means performing a valving function with respect to a space having a gas pressure as low as 2 10 millimeters of mercury and to withstand temperatures as high as 450 C. involved in conditioning the valving means for service at such low pressures without liberating gases occluded in the material thereof.

One object of the invention is to provide an improved valve adapted to function advantageously at relatively low gas pressures and at relatively high temperatures.

A further object is to provide an improved valve wherein a metallic seat thereof is subjected to flow during each closure thereof thereby presenting virgin metal to a valve member during each cycle of valve opening and closure.

Another object is to provide a valve wherein a new seat is automatically provided at each closure thereof.

A further object is to provide a valve wherein a seating member and a valving member are made of materials sufiiciently resilient so as to contribute to a vacuum tight closure of the valve, and to spring back when the valve is opened, to a position different from that during closure, thereby causing a different portion of the valve seat to be engaged by the valve member during each closure of the valve. 7

One valve embodiment according to the invention and which is characterized by the aforementioned desirable features, comprises a tubular valve seat, which when engaged by a valve member, undergoes deformation and flow of the material thereof. Repeated closures of the valve cause the valve member to present material to the valve seat not previously subjected to deformation and flow thus assuring an improved vacuum tight closure. To provide the necessary forced engagement between the valve seat and valve member to produce a desired strain therein to contribute to the maintenance of a vacuum tight closure, and to cause flow of the material of the valve seat, means characterized by an appreciable mechanical advantage may be employed. Such means may comprise a hydraulic system or a mechanical system, for example. The valve seat may be in the form of a relatively short tube made of a suitablemetal such as stainless steel, and having an inner coating of a flowable metal such as copper or silver. The valve member may be in the form of a disc made of a suitable material such as ceramic, molybdenum, or oxidized stainless steel. The

edge of the valve member is tapered about 9 along a The taper of the disc valve member is approximately 9 so that the application of an axial thrust to the valve member results in the application of an appreciable radial force to the valve seat, thereby causing it to enlarge radially, and producing mobility of the material of the portion of the seat engaged by the valve member. The resultant valve closure is effective to isolate a region having a gas pressure as low as 2X10 millimeters of mercury. The material of which the valve seat and valve member are made as aforementioned adapts the valve to withstand outgassing temperatures of 450 C. or higher.

Further objects and features of the invention will become apparent as the present description continues. Reference now to the drawing will reveal that:

FIG. 1 shows a fragmentary elevational cross-section of a valve embodying the invention;

FIG. 2 depicts a sectional view of a valve constituting another embodiment of the invention;

FIG. 3 shows a sectional view of the valve member and valve seat of FIG. 1, and prior to a closure of a valve in which they are incorporated;

FIG. 4 is a fragmentary view in cross-section showing the positions of the valve seat and valve member of FIG. 1 when the valve is closed;

FIG, 5 is a fragmentary sectional view of the valve seat after retraction of a valve member therefrom, and shows in phantom the positions of the valve seat and valve member of FIG. 1 during a subsequent closure of the valve.

The embodiment of the invention illustrated in FIG. 1 constitutes a valve having utility for closing a region 10 from the ambient atmosphere. Walls 11 defining the region aforementioned, are provided with an opening 12 across which a valve 13 is disposed, for successively closing and opening the region 10 to the surrounding atmosphere. The region 10 may be connected to suitable evacuation means, such as mechanical and diffusion pumps (not shown) for evacuating the region referred to, to a gas pressure as low as 2 10- millimeters of mercury. The walls referred to may be made of stainless steel. During evacuation of the region 10, it is necessary to drive out occluded gases, not only from the walls aforementioned, but also from the material of the valve 13 which forms a part of the enclosure for the aforementioned region. If such occluded gases were not driven off, they would constitute a continuing source of gas and defeat the attainment of the low pressure aforementioned. It has been found that the releasable occluded gases are driven off when the parts referred to are baked at a temperature of about 450 C. for about 25 hours, depending on the metal to be outgassed.

The valve 13 may comprise a valve seat in the form of a short tube or ring 14, made of stainless steel, for example, which has one end portion disposed in an annular recess 15 in the top wall 16 of the region 10, to which it may be suitably fixed in vacuum tight manner as by brazing or welding. The valve member 17 may be a disc made of a ceramic such as alumina, or it may be made ofmolybdenum or oxidized stainless steel, for example.

Each of these materials is of advantage in that it is characterized by relatively poor adhesion thereto of the material of the valve seat 14 during an opening of the valve.

As shown in FIG. 3, prior to an initial closing of the valve, the valve seat is cylindrical throughout its length. The valve member is provided with an edge including a cylindrical portion 1-8 and a tapered portion 19..

The valve seat 14 may have a coating 20 of a flowable metal, such as copper, gold or silver, for example, on the inner surface thereof. For lower temperature use, say 250 C., the coating may comprise lead, for example. The internal diameter of the valve seat 14 including seat.

the coating is less than the diameter of the cylindrical portion -18 of the valve member. However, the tapered portion of the valve member adjacent to face 21 thereof, has a diameter that is smaller than the inner diameter of the coated valve seat 14. I

As a consequence, and as shown in FIG. 4, when the valve member is urged axially toward the valve seat 14,

radial expansion of the upper end of the valve seat, occurs. This expansion involves the application of an appreciable radial force by the valve member 17 to the valve seat 14, and causes the corner or edge 22 formed by the merger of the cylindrical and tapered edge portions of the valve member, to penetrate the material of the coating 20 and to produce flow therein. Such ilow has several advantages. It eliminates any bubbles that may have been present in the coating material, and it results in the presentation of a virgin portion of the coating material to the valve member during each closure there- 'of, thereby contributing to a good vacuum-tight engagement between the valve member and'seat.

The radial expansion of the valve seat 14 produced by the axial thrust of the valve member 17, results in a continuing force urging the seat and valve member into closed position after a closure thereof has been effected. This radial force is transmitted along a region which includes an appreciable axially extending part of the cylindrical portion .18 of the valve member edge, and a surface of coating 2d parallel thereto. This parallel coating surface is formed as the consequence of a plastic deformation of the coating 20 by the corner 22 on the valve member when the valve is moved to closed position. This engagement between the edge portion 18 and the coating 20, therefore, is substantiallyfree from any component tending to axially dislocate the valve member 17' from the valve seat 14.

For best results, the corner or ridge 22 should have as small a radius as possible. A relatively sharp or slightly rounded ridge 22 contributes to a desired flow of the metal of coating 22 for a vacuum tight closure of the valve 13, at the relatively low pressures aforementioned.

When the valve member 17 is subsequently removed from seated engagement with the valve seat 14, as shown in FIG. 4, the material of the valve seat springs back slightly, resulting in a reduction of the diameter of the The spring back has been found to be not as great as the magnitude of radial expansion of the seat during a prior valve closure, thus indicating that the expansion was carried slightly beyond the elastic limit of the material of the seat. However, no matter how many closures of the valve take place, the valve seat 14 does not expand a distance greater than the outer diameter of the cylindrical edge portion 13 of the valve member.

Removal of the valve member 17 during an opening of the valve reveals the formation of an annular bulge or concentration 24 of coating material on the inner surface of the valve seat 14. This bulge resulted from the flow produced in the coating material 20 by the valve member 17. As a consequence of the relatively slight taper of the valve member which is about 9 as aforementioned, and the relatively sharp ridge 22 thereon; some coating material remains between the ridge and the valve seat 14, as shown in FIG. 4. The coating remaining in the region, after a closure of the valve, is relatively thin, however, since it is required to absorb the, radial thrust of the valve member on the inner wall of the seat '14. The ridge 2-2 concentrates the thrust refer-red to, to a relatively small area, and contributes to the realization of a vacuum tight closure of the valve.

After a retraction of the valve member 17 from the valve seat 14, as shown in FIG. 5, the bulge 24 of coating mate-rial remains on the seat. However, during a subsequent closure of the valve, wherein the valve member is moved to the position shown in phantom in FIG. 5, the material of the bulge is caused to undergo plastic flow to contribute to the formation of a new bulge. 26.

to no deformation.

It will be noted that the instant closure of the valve has resu-led in farther penetration by the valve member 17 of the interior of the valve seat 14. The need for a plurality of such farther penetrations during a plurality of openings and closures of the valve creates a dependence of the life of the valve on the length of the valve seat 14. Thus, an increased life of valve openings and closures is obtained by an increase the length of the valve seat. valve seat of practical length has permitted a valve life involving some 200 openings and closure-s to be obtained.

It will be realized from thepforegoing that an appreciable force is necessary to cause the valve member 17 to assume a seated position on the valve seat 14. One effective Way of providing such form is by a pneumatic system shown in FIG. 1. A hydraulic system would also serve well. The pneumatic system illustrated in FIG. 1, includes a cylinder 28, mounted on a fixed support and within which is disposed a piston 36. At the lower end of the piston (as shown in FIG. 1) is mounted a valve member -17, by suitable means such as a screw 31. The upper end of the cylinder 28 is provided with an opening 32 communicating with a duct 33. A valve 34 selectively connects duct 33 with a duct 35 communicating with a source of air under pressure (not shown) and a duct 36 connected to a source of air at reduced pressure (not shown). A hand operated knob 37 permits rotation of valve member 38 to effect the desired communication between duct 33 and either of ducts 35, 3 6. Rotation of the knob 37 in a counterclockwise direction from the position shown in FIG. 1 through an angle of connects the duct 33 with duct 36. A return rotation of the knob again places ducts 33 and 35 in communication. When ducts 33 and 35 are in communication, the sources of air under pressure produces a downward thrust on the piston 30 with suflicient force to establish a seated relation of valve member 17 on the seat 14. A subsequent turning of the valve to cause duct 33 to communicate withduct 36 reduces the pressure within the cylinder 28, thereby causing atmospheric pressure to raise the piston, thereby displacing the valve member 17 from its seated position on seat 14, and opening the valve. If atmospheric pressure should prove of insufiicient force to effect the aforementioned disengagement and opening of the valve, the pneumatic system may be modified to selectively connect the source of air under pressure to regions Within the cylinder 28 that are above. and below the piston 30.

To determine the magnitude of the thrust to be applied to the valve member 17 by the pneumatic system referred to, a plurality of dimples 39 may be provided on a side of the valve member and equally spaced in an array parallel to the axis thereof. The dimples are relatively small and may be made of an easily deformable material such as lead. Thus, when the downward thrust of the valve member 17 has proceeded until the lowermost dimple 39 is deformed, it will provide an indication that a sufficient thrust has taken place for a vacuum tight engagement between the valve member 17 and the valve seat 14.

The embodiment shown in FIG. 2 differs from that of FIG. 1 in several respects. The positions of the valve member and valve seat are reversed, that is to say, the movable valve member 42 is deformed during a closure of the valve, and the valve seat 43 is fixed and subject The valve member 42 may be made of material similar to that of valve sea-t 14 discussed in connection with FIG. 1, and the valve seat 43 may comprise the same material as the valve member 17 of FIG. 1. In the foregoing and following description, the movable member of the valve is called the valve member and the fixed member is called a valve seat.

As shown in FIG. 2, the valve member 42 is fixed to a plate 44 by being extended into an annular groove 45 therein and welded in position. The valves seat 43 is extended into the opening 12 in wall 15 and is fixed to the wall by welds 46.

Another respect in which the embodiment of FIG. 2 differs from that of FIG. 1, resides in the means utilized to apply a closing and opening force to the valve constituted by valve member 42 and valve seat 43. This means comprises a mechanical system including a shaft 48, rotationally slidable on plate 44, and having a portion 49 threadedly engaging a plate or bar 50 supported on wall 16 by means of standards 51, 52. The shaft 48 may be integral with a lever 53 having an appreciable length extending laterally of shaft 48. In this Way, rotation of shaft 48 in a given direction by manually engaging the lever 53, in combination with the threaded engagement between the shaft and the plate 50, results in a desired mechanical advantage for advancing the valve member 42 into seated relation with respect to the valve seat 43.

It should be noted in this connection, that While the valve member 17 in FIG. 1 is disc shaped, the corresponding member 43 in FIG. 2 which serves as a valve seat, is ring shaped, and is provided with a flange 55 for engaging the wall 16 conveniently.

In other respects the ring seat 43 is similar to disc valve member 17. Thus the taper 56 in the ring seat 43 is disposed at an angle of about 9 from the axis of the ring and the corner of ridge 58 describes a relatively sharp junction free of any appreciable radius. The valve member 42 in FIG. 5 contracts when in appropriate seated position with respect to valve seat 43. Such contraction involves a radial force as great as that present during the expansion of the valve seat 14 of FIG. 1, in response to an axial thrust of a given magnitude. -The valve member 42 is provided with a coating 60 on the outer surface thereof, which disposes the coating between the valve member 42 and the valve seat 43, when the valve is closed. The coating 60 may be of the same material as the coating 20, of FIGS. 1 and 3. The coating 60 of FIG. 2 undergoes the same plastic flow as coating of FIG. 1, as illustrated more clearly in FIGS. 4 and 5, during a closing of the valve.

In review of the described embodiments there is permanent outward deformation of the seat means. Thus, for example, as pointed out above with regard to to FIG. 4, when the valve member 17 is removed from seated engagement with the valve seat 14, the material of the valve seat springs back slightly, resulting in a reduction of the diameter of the seat, and this spring back is not as great as the magnitude of the radial expansion of the seat during a prior valve closure, the expansion being carried slightly beyond the elastic limit of the material of the seat. In this regard the valve member 17, being a solid, can deform the valve seat 14 beyond the elastic limit of the seat.

Additionally, the seat means has an unretained' elastically deformable portion including an inside plastically deformable metal coating of a first inside diameter for communicating the ambient atmosphere with the chamber at one end of the seat means and the solid ceramic plug means has a uniform cylindrical portion terminating in a first fiat end whose outside diameter is greater than the first inside diameter and has a tapered portion terminating in an end whose outside diameter is less than the first inside diameter, the tapered and cylindrical portions of the plug means intersecting to form a ridge whose outside diameter is greater than the first inside diameter. Also, the diameter of the plug means is so related. to the material and dimension of the seat means so as (thereby) to cause plastic flow of the coating to form a sealing bulge between the plug and seat means, and substantially permanent outward deformation of the seat means to close the chamber from the ambient. To this end, the means for actuating the plug, telescopically thrusts the plug means and ridge to different positions along the inside length of the seat means to cause substantially permanent outward deformation as Well as elastic deformation of the seat means to close the chamber from the ambient and biases the plug means and ridge out of the seat means and for springing the fiowed deformed portion of the seat means inwardly to an inside diameter less than the diameter of the uniform cylindrical portion of the plug means and more than the first inside diameter to communicate the chamber and ambient through the seat means.

It is apparent from the foregoing that an improved valve is provided having advantageous utility under conditions of ultra high vacuum and relatively high temperature. The fact that the valve member of the valve of FIG. 1 and the valve seat of FIG. 2, are tapered, facilitates engagement between the seat and valve members of the valve Without the need for critical alignment thereof. The consequent self-alignment of the seat and valve member expedites a closing of the valve.

A valve incorporating the invention finds utility in any applications wherein it is desired to open and repeatedly close a chamber having an ultra high vacuum condition therein.

Moreover, While the valve illustrated by way of example is designed to open and close a highly evacuated region with respect to the ambient atmosphere, it is apparent that the features discussed in the foregoing will find utility in a valve disposed between a chamber being evacuated and a pumping system, so as to permit closure of the chamber in the event of a pump failure, or for other reasons.

I claim:

A method of valv-ing with a cylindrical, metal tube having opposite first and second open-ends and a plastically deformable metallic coating on its inside diameter between said ends, and a ceramic plug having an outer annular ridge, comprising instrumentally thrusting said plug telescopically into said tube elastically and plastically to deform a first portion of said tube extending from said ridge to said first open end and plastically to flow a first portion of said coating to form a first valve seat bulge between said tube and plug intermediate said ridge and said second open end, instrumentally removing said plug from said first open end, and instrumentally reinserting said plug telescopically into said tube toward said second open end elastically and plastically to deform a second portion of said tube extending from said first portion toward said second open end and plastically to flow a second portion of said coating to form from said first valve seat bulge a second valve seat bulge between said tube and plug intermediate said ridge and said second open end disposed toward said second open end from the position of said first bulge.

References Cited by the Examiner UNITED STATES PATENTS 940,689 11/1909 Hodgkinson 137556 X 1,839,340 1/ 1939 Pittlick 22046 2,192,339 3/1940 Wilson 25l334 3,024,300 3/1962 Martin 29-525 X WILLIAM F. ODEA, Primary Examiner. ALAN COHAN, Examiner. 

